Some Transport Properties of Oxygen-Deficient Single-Crystal Potassium Tantalate (KTaO3)

Hall-effect and electrical-conductivity measurements have been made on reduced single crystals of the perovskite potassium tantalate (KTa${\mathrm{O}}_3$) over the temperature range 1.6-295°K. Lattice scattering predominates above 100°K where the Hall mobility satisfies the empirical expression ${\mu }_H=8\mathrm{}\times {10}^8{T}^{-3\mathrm{}}$ ${\mathrm{cm}}^2$/V-sec. The room-temperature value is 30 ${\mathrm{cm}}^2$/V-sec. Below 100°K, ionized donor and impurity scattering become important, although mobilities as large as 23 000 ${\mathrm{cm}}^2$/V-sec have been observed at 4.2°K. These results are compared with published data for the $3d$ band in isostructural SrTi${\mathrm{O}}_3$ and shown to be consistent with the expected larger overlap of $5d$ orbitals. Free-carrier optical-absorption measurements presented in this paper indicate that electron scattering at room temperature in KTa${\mathrm{O}}_3$ is mainly by the highest frequency longitudinal polar mode situated at approximately 0.12 eV. Dielectric-constant measurements have also been made. These data show an extrapolated Curie temperature of 4±2°K for KTa${\mathrm{O}}_3$ with nonferroelectric behavior at 1.6°K.